[ADT, CSSPGO] Specify set comparer

In _GLIBCXX_DEBUG builds, potentially implicitly enabled by
LLVM_ENABLE_EXPENSIVE_CHECKS, std::set<A, B>::iterator and
std::set<A, C>::iterator are distinct types that are not
interconvertible. This change aligns the iterator types with the set
types.

Reviewed By: hoy

Differential Revision: https://reviews.llvm.org/D119798

Author: hvdijk

llvm/include/llvm/ADT/EquivalenceClasses.h

@@ -161,7 +161,8 @@ class EquivalenceClasses {
   //
 
   /// iterator* - Provides a way to iterate over all values in the set.
-  using iterator = typename std::set<ECValue>::const_iterator;
+  using iterator =
+      typename std::set<ECValue, ECValueComparator>::const_iterator;
 
   iterator begin() const { return TheMapping.begin(); }
   iterator end() const { return TheMapping.end(); }

llvm/include/llvm/Transforms/IPO/ProfiledCallGraph.h

@@ -51,10 +51,10 @@ struct ProfiledCallGraphNode {
     }
   };
 
-  using iterator = std::set<ProfiledCallGraphEdge>::iterator;
-  using const_iterator = std::set<ProfiledCallGraphEdge>::const_iterator;
   using edge = ProfiledCallGraphEdge;
-  using edges = std::set<ProfiledCallGraphEdge, ProfiledCallGraphEdgeComparer>;
+  using edges = std::set<edge, ProfiledCallGraphEdgeComparer>;
+  using iterator = edges::iterator;
+  using const_iterator = edges::const_iterator;
 
   ProfiledCallGraphNode(StringRef FName = StringRef()) : Name(FName) {}
 
@@ -64,7 +64,7 @@ struct ProfiledCallGraphNode {
 
 class ProfiledCallGraph {
 public:
-  using iterator = std::set<ProfiledCallGraphEdge>::iterator;
+  using iterator = ProfiledCallGraphNode::iterator;
 
   // Constructor for non-CS profile.
   ProfiledCallGraph(SampleProfileMap &ProfileMap) {